The present invention relates to a liquid crystal display device, a display device, and a backlight device, and more particularly to a solid-state-light-emitting-element (LED) direct backlight device which is mounted on a back surface side of a display device and irradiates a light-source light to the display device and the display device which uses the backlight device.
Recently, as a backlight used in a large-sized liquid crystal television set, a large-sized monitor or the like, a cold cathode fluorescent lamp has been mainly popularly used. The backlight device which uses the cold cathode fluorescent lamp is roughly classified into a side-edge type backlight device which arranges a cold cathode fluorescent lamp on a side of a light guide body and a direct backlight device which arranges a plurality of cold cathode fluorescent lamps in parallel on a back surface of a liquid crystal display panel without arranging a light guide body.
While having an advantage that the side-edge type backlight device can have the relatively compact shape, the side-edge type backlight device has a drawback that the light utilizing efficiency is low. On the other hand, while having the high light utilizing efficiency, the direct backlight device increases a thickness thereof. To replace the backlight device which uses such a cold cathode fluorescent lamp as a light source, recently, a backlight device which uses a solid-state light emitting element (LED) represented by a light emitting diode which exhibits the high color reproducibility and the rapid responsive speed and uses no mercury to satisfy the demand for the preservation of environment as a light source has been studied and developed by concerned companies.
Recently, as a solid-state light emitting element, a solid-state light emitting element which is capable of emitting three colors consisting of R (red), G (green), B (blue) and a solid-state light emitting element capable of emitting white color have been developed. With respect to the solid-state light emitting element which is used as a light source of a backlight device, since it is desirable to irradiate a white light to a display panel eventually, the use of the solid-state light emitting element capable of emitting the white color light is considered. However, the white solid-state light emitting element which irradiates the white light obtains the white light by converting the color emitted from the blue-light solid-state light emitting element or the ultraviolet-light solid-state light emitting element into the white color using phosphors and hence, there arises a drawback that the white color solid-state light emitting element exhibits the poor color rendering and narrows a range of color reproducibility.
On the other hand, the solid-state light emitting elements capable of emitting lights of three colors consisting of R (red), G (green), B (blue) is superior to the white solid-state light emitting element with respect to a point that three-color-light-emitting solid-state light emitting element can obtain the wide range of color reproducibility and a point that by changing a current quantity of the solid-state light emitting elements capable of emitting lights of three colors consisting of R (red), G (green), B (blue), chromaticity of the backlight can be freely changed. From this viewpoint, it is preferable to use the solid-state light emitting elements capable of emitting lights of three colors consisting of R (red), G (green), B (blue) at this stage.
With respect to the constitution of the backlight device which uses the solid-state light emitting elements capable of emitting lights of three colors consisting of R (red), G (green), B (blue) as a light source, the solid-state light emitting elements capable of emitting lights of three colors consisting of R (red), G (green), B (blue) may be arranged on a back surface of the display panel and this constitution is shown in FIG. 19 which is a developed perspective view of an essential part. As shown in FIG. 19, on a back surface of the liquid crystal display panel which, for example, constitutes the display panel, a solid-state light emitting element array ALL which mounts the solid-state light emitting elements LED capable of emitting three colors consisting of R (red), G (green), B (blue) thereon is arranged, a reflector REF10 is arranged on a back surface of the solid-state light emitting element array ALL, and side reflectors REF11, REF12, REF13, REF14 are arranged on side-surface-side.
Further, an optical sheet stacked body OPS is arranged above the solid-state light emitting element array ALL by way of an air layer ARL, wherein the optical sheet stacked body OPS is formed by stacking a first diffusion sheet DF1, a first prism sheet PRZ1, a second prism sheet PRZ2 and a second diffusion sheet DF2 in this order from the solid-state light emitting element array ALL side. Further, between this optical sheet stacked body OPS and the solid-state light emitting element array ALL which mounts the solid-state light emitting elements LED capable of emitting lights of three colors consisting of R (red), G (green), B (blue) thereon, an air layer ARL which has a relatively large layer thickness is arranged.
In the backlight device having such a constitution, the light which is emitted from the solid-state light emitting elements LED capable of emitting lights of three colors consisting of R (red), G (green), B (blue) which constitutes the light source is subjected to the color mixture using the air layer ARL, the reflector REF10 and the side reflectors REF11 to REF14 and, thereafter, the light is irradiated to, for example, the back surface of the liquid crystal display panel which constitutes the display panel.
The constitution which uses the solid state light-emitting element as a light source of the backlight device is disclosed in a following literature 1. Further, the constitution which irradiates the white light to the liquid crystal display panel by performing the color mixture using the solid-state light emitting elements capable of emitting lights of three colors consisting of R (red), G (green), B (blue) as the light source is disclosed in a following literature 2. Still further, the constitution which arranges a light guide for color mixture on a back surface side of a light guide body is disclosed in a following literature 3.
That is, the display device which uses light emitting diodes which constitutes the light emitting elements in the light guide body as the light source is disclosed in, for example, Japanese Patent Laid-Open 109421/2003 (literature 1), SID 02 DIGEST “40.5L: Late-News Paper: 18. 1-inch XGA TFT-LCD with Wide Color Reproduction using High Power LED-Backlighting (literature 2), and S-12. “LCDbacklight light source with high color reproducibility”, the 36th Nation-wide Convention, Japan Illumination Association, Heisei 15(2003) (literature 3).